Food and drink doesn't come cheap when you're hosting 600 guests for lunch and another 200 for dinner.

However, the royals aren't expected to go overboard, according to Niemierko, who has worked on weddings attended by Prince Harry.

"The royals don't spend as much as everyone thinks they do. They're not the Kardashians," he said.

Niemierko estimates the Queen -- who is hosting the afternoon reception -- will spend £100 ($135) per person for her 600 guests. That puts the cost at £60,000 ($81,500).

The evening reception, hosted by Harry's father Prince Charles, could cost around £250 ($340) per head, he said. That puts the price at £50,000 ($68,000) for 200 guests.